Warm gas towards young stellar objects in Corona Australis - Herschel/PACS observations from the DIGIT key programme

Author(s)

Johan E. Lindberg, Jes K. Jørgensen, Joel D. Green, Gregory J. Herczeg, Odyssefs Dionatos, Neal J., II Evans, Agata Karska, Susanne F. Wampfler

Abstract

The effects of external irradiation on the chemistry and physics in the

protostellar envelope around low-mass young stellar objects are poorly

understood. The Corona Australis star-forming region contains the R CrA

dark cloud, comprising several low-mass protostellar cores irradiated by

an intermediate-mass young star. We study the effects on the warm gas

and dust in a group of low-mass young stellar objects from the

irradiation by the young luminous Herbig Be star R CrA. Herschel/PACS

far-infrared datacubes of two low-mass star-forming regions in the R CrA

dark cloud are presented. The distribution of CO, OH, H2O, [C II], [O

I], and continuum emission is investigated. We have developed a

deconvolution algorithm which we use to deconvolve the maps, separating

the point-source emission from the extended emission. We also construct

rotational diagrams of the molecular species. By deconvolution of the

Herschel data, we find large-scale (several thousand AU) dust continuum

and spectral line emission not associated with the point sources.

Similar rotational temperatures are found for the warm CO ($282\pm4$ K),

hot CO ($890\pm84$ K), OH ($79\pm4$ K), and H2O ($197\pm7$ K) emission,

respectively, in the point sources and the extended emission. The

rotational temperatures are also similar to what is found in other more

isolated cores. The extended dust continuum emission is found in two

ridges similar in extent and temperature to molecular mm emission,

indicative of external heating from the Herbig Be star R CrA. Our

results show that a nearby luminous star does not increase the molecular

excitation temperatures in the warm gas around a young stellar object

(YSO). However, the emission from photodissociation products of H2O,

such as OH and O, is enhanced in the warm gas associated with these

protostars and their surroundings compared to similar objects not

suffering from external irradiation.

Organisation(s)

Department of Astrophysics

Publication date

11-2013

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

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